Many electrical devices such as cell phones, personal digital assistants (PDA's), laptops, etc. are powered by a source of relatively low-voltage DC power. Because power is generally delivered through a wall outlet as high-voltage AC power, a device typically referred to as a power supply or power converter is required to transform the high-voltage AC power to low-voltage DC power.
Power supplies are typically constructed by mounting electronic components onto a printed circuit board (PCB). One of the electronic components often included in a power supply is a transformer. During operation the transformer allows the transfer of energy between an input side (referred to as a primary side) of the power supply and an output side (referred to as the secondary side) of the power supply. The input and output sides of the transformer are typically galvanically isolated. Galvanic isolation occurs when DC current is unable to flow between the input side and output side of the power supply.
The construction of a transformer may include winding coils of wire around a structure called a bobbin. The bobbin provides support for the coils of wire and may also provide an area for a transformer core to be inserted such that the coils of wire encircle the core. The transformer core defines a path for a magnetic field generated by an electric current flowing through the coils of wire. A coil wound bobbin configuration that uses a bobbin to support the conducting coils may often be made from ordinary wire.
Typically, the physical height of a power supply is limited by the size of the electronic components mounted on the PCB plus a pin protrusion distance (i.e., the distance that the leads of the electronic component protrude past the solder side of the circuit board). Often, the transformer is the tallest component of the power supply. Thus, the minimum height of the power supply may be primarily limited to the height of the transformer plus the additional thickness of the PCB itself plus any additional pin protrusion.